Interferons (also referred to as “IFN” or “IFNs”) are proteins having a variety of biological activities, some of which are antiviral, immunomodulating and antiproliferative. They are relatively small, species-specific, single chain polypeptides, produced by mammalian cells in response to exposure to a variety of inducers such as viruses, polypeptides, mitogens and the like. Interferons protect animal tissues and cells against viral attack and are an important host defense mechanism. In most cases, interferons provide better protection to tissues and cells of the kind from which they have been produced than to other types of tissues and cells, indicating that human-derived interferon could be more efficacious in treating human diseases than interferons from other species. Interferons may be classified as Type-I, Type-II and Type-III interferons. Mammalian Type-I interferons include IFN-α (alpha), IFN-β (beta), IFN-κ (kappa), IFN-δ (delta), IFN-ε (epsilon), IFN-τ (tau), IFN-ω (omega), and IFN-ζ (zeta, also known as limitin). Interferons have potential in the treatment of a large number of human cancers since these molecules have anti-cancer activity which acts at multiple levels. First, interferon proteins can directly inhibit the proliferation of human tumor cells. The anti-proliferative activity is also synergistic with a variety of approved chemotherapeutic agents such as cisplatin, 5FU and paclitaxel. Secondly, the immunomodulatory activity of interferon proteins can lead to the induction of an anti-tumor immune response. This response includes activation of NK cells, stimulation of macrophage activity and induction of MHC class I surface expression leading to the induction of anti-tumor cytotoxic T lymphocyte activity. In addition, interferons play a role in cross-presentation of antigens in the immune system. Moreover, some studies further indicate that IFN-β protein may have anti-angiogenic activity. Angiogenesis, new blood vessel formation, is critical for the growth of solid tumors. Evidence indicates that IFN-β may inhibit angiogenesis by inhibiting the expression of pro-angiogenic factors such as bFGF and VEGF. Lastly, interferon proteins may inhibit tumor invasiveness by affecting the expression of enzymes such as collagenase and elastase which are important in tissue remodeling.
Interferons also appear to have antiviral activities that are based on two different mechanisms. For instance, type I interferon proteins (α and β) can directly inhibit the replication of human hepatitis B virus (“HBV”) and hepatitis C virus (“HCV”), but can also stimulate an immune response which attacks cells infected with these viruses.
The method of administering interferon is an important factor in the clinical application of this important therapeutic agent. Systemic administration of interferon protein by intravenous, intramuscular or subcutaneous injection has been most frequently used with some success in treating disorders such as hairy cell leukemia, Acquired Immune Deficiency Syndrome (AIDS) and related Kaposi's sarcoma. It is known, however, that proteins in their purified form are especially susceptible to degradation. In particular, for interferon-β, the primary mechanism(s) of interferon degradation in solution are aggregation and deamidation. The lack of interferon stability in solutions and other products has heretofore limited its utility. Therefore, a more effective method of modulating the level of interferons, such as interferon-β, is needed.